Torque sensors are sensors that determine torque by deformation of a measuring body. Most torque sensors operate with strain gauges. There are also torque sensors, which operate on the piezoelectric, the magneto-elastic or the optical principle.
Torque sensors are used on rotating or stationary shafts for the determination of the transmitted torque, but also in calibrating devices for torque wrenches. For short build and very stiff tools to be calibrated, such as torque wrenches, often so-called torque measurement flanges are used. The torque measurement flanges as generic torque sensors consist of an inner hub that is connected by several spokes to an outer ring. The spokes wear sensors, such as strain gauges that measure the bending load at an applied torque. In such torque sensors the influence of lateral forces and lateral moments should be compensated as far as possible. Moreover, the torque sensor should be characterized by low mass moment of inertia and high measuring sensitivity.
With a torque sensor according to the German patent DE 42 08 522 C2 not bending forces, but shear forces are measured. To this end the torque sensor has an inner body or inner hub and a concentric outer annular body. The inner body is connected to the outer annular body by webs extending in star shape. The measuring sensors, for example strain gauges are seated on the webs for the detection of torsion.
In the German patent application DE 195 25 231 A1 a torque sensor is described, which consists of two opposing flanges that are interconnected by webs. Strain gauges are provided on the connecting webs. The cost of this variant of torque sensors are also relatively high. In addition, the dynamic behavior of such torque sensors is very inadequate. A further disadvantage of the torque sensor described therein is, that a shift of the zero point still occurs at high rotation speeds, and that the manufacturing costs of such torque sensors are extremely high.
DE 202 09 850 U1 discloses a torque sensor with webs and having an inner body and an outer annular body concentrically surrounding the inner body. Webs with different widths connect the inner body with the annular body in a star shape. Measuring elements, which are provided on the webs, determine the torsion of the webs generated by an applied torque.
A disadvantage of the aforementioned torque sensors is that the manufacturing cost of the torque sensors is correlated with their accuracy.
Thus, it has been long felt and unsolved need to create a torque sensor, which eliminates the disadvantages of the above-mentioned state of the art and is designed as cost-effective and simple as possible and yet sensitive and accurate.